1. Field of the Invention
The invention is related to the field of communication networks and, in particular, to charging in LTE/EPC communication networks for non-roaming and roaming scenarios.
2. Statement of the Problem
Service providers typically provide numerous voice and/or data services to subscribers using one or more wireline and/or wireless communication networks. Exemplary services include cellular telephony, access to the Internet, gaming, broadcasting or multicasting of audio, video, and multimedia programming, etc. Mobile devices, such as cell phones, personal data assistants, smart phones, pagers, text messaging devices, global positioning system (GPS) devices, network interface cards, notebook computers, and desktop computers, may access the services provided by the communication networks over an air interface with one or more base stations. Communication between the mobile devices and base stations are governed by various standards and/or protocols, such as the standards and protocols defined by the 3rd Generation Partnership Project (3GPP, 3GPP2).
The service providers use offline and online charging functions to keep track of the charges incurred by each device for using the various services. The 3GPP/3GPP2 standards groups have defined a set of specifications that may be used to implement online charging systems and offline charging systems to cover charging in the various network domains (e.g., a circuit switching network domain, a packet switching network domain, and/or a wireless domain), IP multimedia subsystems, and emerging 3G/OMA application services.
Online charging is generally defined as a charging mechanism where charging information can affect, in real-time, the service rendered, and therefore a direct interaction of the charging mechanism with session/service control is needed. In online charging, charging information for network resource usage is collected concurrently with the resource usage. However, authorization for the network resource usage must be obtained by the network prior to the actual resource usage. The network elements in a communication network include Charging Trigger Functions (CTF). For online charging, the CTF triggers on charging events, collects charging information pertaining to the charging events, and assembles the charging information into matching charging events. The CTF then transmits credit request messages to the Online Charging System (OCS) to obtain authorization for the charging event/network resource usage requested by the user. The CTF delays the actual resource usage until permission has been granted by the OCS. When a granted quota of service units is obtained from the OCS, the CTF performs budget control during the resource usage. The CTF enforces termination of the end user's resource usage when permission by the OCS is not granted or expires.
Offline charging is generally defined as a charging mechanism where charging information does not affect, in real-time, the service rendered. In offline charging, charging information for network resource usage is collected concurrently with resource usage. The CTF triggers on charging events, collects charging information pertaining to the charging events, and assembles the charging information into matching charging events. The CTF then transmits accounting messages to a Charging Data Function (CDF).
There are a variety of types of networks operable to provide voice and data communications for mobile users. One present project within the 3GPP is the Long Term Evolution (LTE) which is a project to improve the UMTS mobile phone standard to cope with future requirements. The architecture defined by this project is referred to as the Evolved Packet System (EPS). The EPS architecture comprehends E-UTRAN (Evolved UTRAN) on the access side and EPC (Evolved Packet Core) on the core side.
One problem with LTE/EPC networks is that charging (i.e., a charging architecture and function) has not been effectively defined in detail. 3GPP TS 32.820 describes high level charging requirements for LTE/EPC networks in roaming and non-roaming scenarios. 3GPP TS 32.820 has copied the Packet Domain (PD) charging architecture and the WLAN charging architecture from 3GPP TS 32.251 and 32.252, respectively, but does not adequately describe charging in an LTE/EPC communication network or adequately describe an LTE/EPC charging architecture. Thus, network operators and designers are unsure how to implement online and offline charging in LTE/EPC communication networks.